Acoustic device



July 19, 1932.

J. P MJNTON ETAL ACOUSTIC DEVICE Filed July 20, 1925 5 Sheets-Sheet 1v INVENTORS JOHN P. M\NTON AND BY( ABRHAM/. RINGEL g//LQ A /uuy A ORNEY July 19, 1932- J. P. MlNToN ET AL ACOUSTIC DEVICE Filed July 2O 1925 I5 Shee1',S-Sheeb vl 2 INVENTORS JOHN P. MINTON Aun BRAHM 5Y UNGEL BY fm W AT RNEY 76H25 PEE ffl'/VD Jub' 19, 1932. J. P. MINTON ET ALV ACOUSTIC DEVICE Filed July 2O 1925 3 Sheets-Sheet Patented July- 19, 1932 UNITED STATES PATENroFI-'ICE i JOHN PRESTON MINTON, OF WHITE PLAINS, AND ABRAHAM S. RINGEL, F BROOKLYN,

NEW YORK, ASSIGNORS TO RADIO CORPORATION OF AMERICA,

DELAWARE A CORPORATION 9F ACOUSTIC DEVICE Application filed July 20,

This invention relates to acoustic devices for use in reproduction of voice, music or other signals. It has for its object also the truer and more exact reproduction, constancy of volume and in general more faithful likeness to the original than heretofore.

It has been known that whenever a vibration was impressed upon any vibratile body that there are certain frequencies at which 10 reproduction will be most efficient While at all others more or less inefficiency occurs resulting in exaggeration' of certain tones as well as other undesirable effects. This invention attempts to obviate these difliculties by so arranging the oscillatory member or members that different elements thereof will respond at their most eicient period of vibration at different frequencies thereby causing the reproduction to be more uniform and of a more constant volume as wellas giving greatersensitivity and efficiency.

This kinvention also relates to telephony, telegraphy, and their other allied arts. More specifically the arrangements herein disclosed represent what is commonly known as loud speakers or electrical reproducers and the like although it is not intended to limit its use to this particular field. It might Vas well be used with phonographs and other resonant rever-- berating systems. It is also useful wherever large amplitudes of vibration are desired at or within the audio frequency range which must necessarily be of constant value.

Other objects and advantages will be apparent upon reading the following disclosure including specification, claims and annexed drawings.

The various 4gures of the drawings show different specific details as follows Fig. 1 shows the front view of one modification. Fig. 2 shows a cross section of this modification along lines II--II of Fig. 1. Fig. 3 shows a different adaptation of the same idea.

Fig. 4 shows a cross section-of the adaptation of Fig. 3 along the lines I V-IV.

Figs. 5 and 7 are graphs of various characteristic curvesl of some'of these arrangements.

Fig, 6 shows a` simplified arrangement.

1925. Serial No. 44,735.

Fig. 8 shows, in detail, one of the elements used in Fig.. 2dor any detail. Y

Fig. 9 shows another eddy-current operated device. l

These figures make use-of various and differently cnstructed -oscilla-tory elements at tach'ed to the same vibrating system. 1 and 2 of Fig. 1 show two such members mounted in a mounting plate 3 which serves to prevent the vibrations at the rear from affecting those in front. In one instance 1 may bein the form of a diaphragm held rigidly at its periphery while 2 .is a conical member loosely mounted in the mounting plate 3 by means of a thin sheet 11 of fabric, rubber or leather. These two vibratile members are both connected to a common vibrating system by means of connections 12, 17 and 18. 12 may be a light weight rigid spider or other equivalent construction. The lever 7 ofthe vibrating system is suspended at l'about which it freely oscillates. The lever is actuated by the flow of current through the coil 5 mounted on the permanent or electromagnet 8 which causes motion of armature 9 connected to the lever 7 by means of a pivot connection 13. The 4connections 17 and 18 are fastened to lever 7 by means of pivots 14 and 15.

From this construction it can be seen that these two elements may havediferent char: acteristics which so cooperate as to produce a sound which vmay be more nearly constant for a given range of frequencies The cone 2 may be constructed of some semi-rigid fabric such as paper, parchment, cardboard or other membranous material. The cone or diaphragm 1 may be stretched or held loosely and may be of metal or the same material as the cone 2, The `characteristics of this arrangement will be discussed further in con-k 90 nection with Fi g. 5. 1 may also be composed of a compound cone and loosely mounted b similar material 11.l This cone can be 'a justed in such a way that the most pronounced frequencies at which it responds may 95 be varied throughout the range. This is done by an adjustment 10 connected between the two sections of the member. 21 and 22 of Figs. 3 and4 are also diaphragms constructed of similar material and 3 mounted 'in a similar Way as cone 2 ;l 11 being resilient fabric. This fabric is connected to the cylindrical members 19 and 20 which support these cones 21 and 22 to some extent, and

serve to prevent vibrations from the rear of the cones from effecting those on the front. 25 is a magnet permanently or otherwise energized by coils 26 and 50.and 27 and 28 are actuating coils for cones 21 and 22 respectively and are rigidly connected thereto. These coils 27 and 28, located in their rcspective fiux -gaps of the magnet 25 are very sensitive to the slightest change in current.l It is not intended to limit 'this arrangement to the `use of cylindrical mounting members but the cones might as well be mounted as in Figs 1 and 2. 23 is a liexible .disc with spirally cut holes to give it added resilience. Itis fastened at its scenterby .means of a screw or rivet 24 to the middle pole of magnet 25 and helps to center the.

vibrating system.

If the apparatus shown in Figs. 2 and 4 be analyzed and the characteristics of their yva rious elements be plotted taking the audibility as ordinates and the frequency in cycles per second for abscis'sa, curves something like those shown in Fig. 5 will result.

cone 22 of Fig. 4 and curve II shows that of cone 2 of Fig. 2 or cone 21 of Fig. 4. If these two cones in either modiication are operated jointly by the same source or bythe same current the twocharacteristic curves will be superimposed upon each other giving a resultant curve III which shows a smaller percentage of variation and no valleys as a and b. By adjusting diaphragm 1 of Fig. 2

through adjusting nut 10 the characteristic curve I can be shifted horizontally along the abscissa to such a position that it Will most completely eliminate the silent periods or valleys.

i These two ideas may be combined into one structure' as shown 1n Fig. 6 where 3 1s the teristicof the cone 29 and II that of the disc4 or diaphragm 30. In this case thel valley a is lled by the hump in the curve II thus producing 'the more nearly constant response shownl in III.

yThe adjustable' feature of 1 in Fig. 2 is shown in detail in Fig. 8 where 10 is the 'adjusting mechanism comprising threaded shaft' 36 on the adjust-ing bushing .39 and locknut 38 being threaded or. the shaft 36. The end of this shaft is connected lto seat 40 Curve Il shows a characteristic of cone 1 of Fig. 2 or which is attached to the cone 35. 'The two cones 34 and 35 -may have the same slope or different slopes to render them resonant to different frequencies as desired and are fastened together and flexibly mounted in the casing 44 by means of element 46 which may be similar to 11. The cover 45 is screwed in to the casing 44 to conduct the sound or may be omitted as desired. The member 46 is clamped bymeans of bolts 47. A The cones maybe set in vibration by means of magnet 42 connected to casing -44 by the screws 48 and operates on the armature 4l which is rigidly attached to the cone 35.

By means of the shaft 36 different tensions may be applied to the compound cone either in contraction or expansion thereby changing the periods at which it responds' most'elliciently. In thisway'the characteristics may be varied at will.

Another modification of this idea is shown in Fig. 9. As in the case of Fig. 4 a similar magnetic structure 49 is used with the exception of the location of 'the actuating coils 51 and 53 which are mounted in' the pole pieces themselves instead of being mounted on the Cones\ The magnetic structure 49 may be either permanently or electrically energized as by means of coils 26 and 50. The current through these coils must be direct in order to give approximately constant'flux.

The flux produced through the air gaps passes between the respective pole pieces. In

the air gaps are located cylindrical sleeves 52 and 57. These .sleeves maybe of copper, aluminum or other low resistant electrically conductive material, ormay bein the form of multi-turn short circuited coils mounted on `proper brackets. As shown in the figure, cylindrical sleeves are used, riveted by means of rivets 55 to different parts of the cone 54 or fastened by any other suitable means.

It has been found best to makethese sleeves as light as possible in lorder that they may respond to high frequencies more readily without absorbingtoo much energy by .their 4current will cause the flux llowingacross the gaps Idue to the coils 26 and 50 to be shifted backand forth in a ldirectionv parallel to the sleeves 52 and 57. .Due to the fact that these' Other elements 3 t.

sleeves are ofconducting material eddy cur-.

rents will be setup in the sleeves which at' tempt to counteract this effect. In this at tempt a reaction will be exerted upon the Sleeves themselves moving them with the vibrations of the ux thus :moving the cone correspondingly.

As shown the sleeve 52 is connected to an outer part of cone g4 and therefore will pro. duce a greater response to vibrations of lower frequency while sleeve 57 being connected to one end of the cone will bemore responsive to vibrations of a higher frequency producing nodes and anti-annodes along the length of the cone 54. It can thus be seen that the two actuating sleeves will, in connection ,with the cone be responsive toldifferent resonant frequencies thereby causing a more constant response than would be obtainable with a single operator. The characteristics of this system would bel-similar to those described in connection with Figures 3, 5 and 8.

Any other combination arrangements of different vibrating systems inay be used as for instance cone 1 of Fig. 2 may be used in conjunction with the device of Fig. 4 or with a diaphragm. Three or more vibrating .systems may also be used in order to make the audibility curve more constant in value over a very wide frequency range. With such a combination, is used a longer lever 7 as the case may require and the various systems may be attached at expedient points. Each syssuch as a magnet and armature and the operators connected into the saine circuit. It is not intended to limit the constructions of these arrangements to the specific modifications shown but any other elemeiitsmay be used which are well known and the characteristics of which are known to take the place of those shown. The greater the number of elements used and the more diversified their maximum values of audibility arein respect to frequency` the more constant will be the response. This arrangement also could be used with a phonograph or other similar device by attaching a needle or reproducer to the oscillating system in a well known manner.

I request protection according to the following claims 1. The method of reproducing oscillations of different frequencies which consists in iinpressing these oscillations upon elements having different natural responses and Vcombining the responses thus produced whereby a constant response results and preventingr the oscillations developed on both sides of the elements from intermingling.

2. A method of producing oscillations which consists in vibrating a resonant body having a period of minimum response between two periods of max-imum response, and producing other oscillations which are most effective at the period of minimum response" 8. A method of producing oscillations which consists in vibrating a resonant body having a period ,of maximum response at a low frequency 4and a second period of maximum response at a high frequency andin simultaneously vibrating a second resonant body having a period of maximum response intermediate the periods of maximum response of the4 first mentioned resonant'body.

4. In combination, a vibratile element having a maximum response at low frequencies .and alsoat high frequencies, a second vibratile element having la maximum response at intermediate frequencies and means for vibrating both elements simultaneously.

5. An acoustic device comprising a vibratile element having a maximum response at low frequencies and also at high frequencies, a second vibratile element having a maximum response at intermediate frequencies and a single mechanism for vibrating said elements Lsimulta'neously and in phase.

6. In combination, a vibratile element having a maximum response at llow frequencies and also at high frequencies, another vibratile element having a maximum response at intermediate frequencies, means for vibrating both elements simultaneously whereby a constant response may be obtained and means for adjusting one of the elements to vary its period of maximum response.

7. An acoustic device comprising a vibra-` tile element having a maximum response at low frequencies and also\at high frequencies, a second vibratile element having a maximum response at intermediate frequencies, and means for vibrating said elements simultaneously, said means comprising a lever pivoted at one end, a driving unit connected to said lever intermediate its ends, and connections from said' lever to said vibra-tile elements.

8. In combination a vibratile element having a maximum response at low frequencies and also at high frequencies,another vibratile element having a maximum response at intermediate frequencies, means for vibrating both elements simultaneously at the saine frequency whereby a constant responseo may be obtained, and means for adjusting one of the elements to vary its period of maximum responsegjone of the elements having a flexible support?y y 9. A vibratile member for an acoustic device comprising a pair of conical diaphragms positioned with their edges adjacent each other and means adjustable from outside of ls'a/id diaphragme for tensioning said diaphragms. r

10. A vibratile member for an acoustic device comprising al pair of conical diaphragms positioned with their edges adjacent .each other and means for tensioning said diaphragms, said means comprising a member ixdlysecured to the apex of one conical diaphragm and adjustably secured to the apex of the second conical diaphragm. 1 l1. An acoustic device comprising a casing,

a vibratile member, resilient means for supiso Iportin said lvibratile member-in said cashing, said vlbratile member comprising a pair of cones positioned with their edges-in contact with each other and with their apexes oined by means of an adjustment member, one end of said adjustment member comprising an armature, and a driving unit securedto said casing and cooperating with said armature.

l12. In an acoustic device, a diaphragmy vmounted for vibration, a lever of the third class, means connecting said diaphragm wlth said lever, and means for vibrating said lever.

13. An acoustic device comprising a diaphragm of the type adapted to radiate sounddriving unity connected to said lever.

15. An acoustic device comprising amounting-provided with alplurality of openings, a diaphragm for each opening, iexible means for supporting said diaphragms within said openings, and means for vibrating said dia- Y lphragms simultaneously.

' 16. Anacoustic device comprising a mounting provided with a plurality of openings, a

diaphragm for each opening, flexible means f for supporting saiddiaphragms within said openings, and a singlemeans for mechanical-l sheets of thin material juxtaposed to form a hollow vibratory member decreasingy inv thickness from its centre toward its periphery, means for simultaneously separating and stretching'said sheets, said means being supportedsolely by said vibratory member and vibratile therewith.

23. The combination of an acoustic diaphragm, comprising two sheets of thin material, means for securing said sheets together at their peripheries and rigidly supporting them, and means for separating the centers of said sheets and holding them in fixed vibratory relation with respect to each other, saidmeans being adjustable to vary the distance between the centers of said sheets and thereby vary their tension.

24. A loud speaking diaphragm comprising a stretched flexible sheet held constantly '85' under tension along its surface, and a driving member connected to the center of sa1d diaphragm, the normal tensioned condition of the diaphragm imposing substantially no pull or push load on the driving member.'

v 25. A sound reproducer comprising a membrane, means for holding the same constantj ly under tension along its vibratory surface; and a driving unit connected to the center of said membrane which is supported under tension independently of said driving unit.

.JOI-IN vl?. MINTON. ABRAHAMS. B INGEL.

ly vibrating said diaphragms simultaneously and in phase.

17. A vibratile unit for an acoustic device comprising a vibratile element of conical formation and a diaphragm connected therewith.

18. A vibratile unit for an acoustic device comprising a frustum and a'diaphragm secured to one end thereof.

19. In an acoustic device, a vibratile unit comprising a` tapered portion and a plane portion secured to one end thereof, and means for vibrating said unit.

20. A vibratile unit for an acoustic device comprising a conical portion having a maximum response at'low frequencies and also at high frequencies, and a flat portion secured to said conical portion, said flat portion havingl a maximum. response at intermediate fre'- quencies.

- 21. An acoustic diaphragm comprising two circular metallic sheets oined together at the periphery of one of said sheets, and screw means associated with said sheets 4to adjust the tension therein and to hold said sheets in spaced and iixed vibratory relation.

22. An acoustic diaphragm' comprising two DISCLAIMER 1,868,019-John Preston Minton, White Plains, and Abraham S Ringel, Brookl n, N .Y. ACOUSTIC DEVICE. Patent dated Jul 19, 1932. -Disclaimer filedv ay 510, 1933,by theirst named patentee, John Minton.; 1

Hereby enter `this disclaimer to that part of the joint application directed to Figs. 3,-4, and. 9 thereof and to the subject matter'of applications Serial Numbers 263,377 and 263,378 filed in the name of Abraham Ringell as divisio al application 'of said application S. N. 44,735 to coverthe subject matter of Figs. 4, anl 9 of said w application S. N. 44,735, now Patent1,868,019. v

[Oficial Gazette June 1 3, 1933.] 

